I tested Flume in last week with ScribeSource(https://issues.apache.org/jira/browse/FLUME-1382) and HDFS Sink. Moredetailed conditions and deployment cases listed below. Too many 'Full GC'impact the throughput and amount of events promoted into old generation. Ihave applied some tuning methods, no much effect.

The Flume agent was run on its own physical machine in a single JVM. Aseparate client machine generated load against the Flume box inList<LogEntry> format. Flume stored data onto a 4-node HDFS clusterconfigured on its own separate hardware. No virtual machines were used inthis test.

By analyzing JVM Heap, we found that there are many LogEntry objects inOldGen. We have tried to carry out some optimizations, but the results arenot satisfactory. We will continue to track this limitation.

Please set XMX and XMS as the same (4GB here), because on high traffic sinks it could be that the allocation process can cause a gc sweep. Also I would recommend to define the gen sizes with:-XX:NewSize=64m -XX:MaxNewSize=64m